How do I change the amount of places before a decimal when a number is printed in scientific notation? (i.e. 10e6 rather than 1e7)

I currently print a number to the command window using something like this:

fprintf('%.2e',1000)

This will print out as:

1.00e+3

What I want it to print out as is:

10.00e+2

How do I do this?

[Stephen23]

https://www.mathworks.com/matlabcentral/answers/892-engineering-notation-printed-into-files

https://www.mathworks.com/matlabcentral/fileexchange/63928-num2eng-fast-number-to-engineering-notation-si-conversion

Search this forum and FEX for more.

Answer 1

[Walter Roberson]

You would have to write the code for this yourself; MATLAB does not have provision for this.

Question: under what circumstances should there be two leading digits? For example, how should 0 be printed out? How about 5.3 -- should that be formatted as 53.00e-1 ?

[Franklin Turbeville]

For my research in a wind tunnel facility, we often talk about Reynolds number in millions. So it would make sense to have 5e6 compared to 10e6, rather than 5e6 and 1e7.

[Franklin Turbeville]

I was hoping that there would be an easy solution like there is for precision. Thanks for the response.

[Walter Roberson]

Engineering notation usually goes by 10^multiple of 3, which is not the same thing you were talking about; you had wanted 1000 to come out like 10.0e2 but in engineering notation it would be 1.0e3

Answer 2

[Star Strider]

Try this:

a = 1000;
n = 2;
expstr = @(x,n) [x*10.^(-n*floor(log10(abs(x))/n))  n*floor(log10(abs(x))/n)];
Result = sprintf('%.2fE%+04d', expstr(a,n))

Result =
    '10.00E+002'

I wrote this little ‘expstr’ utility function to produce the mantissa and exponent for my own use a few years ago. The first argument ‘x’ is the number, and the second ‘n’ is the resolution you want. It returns a (1x2) vector with the mantissa as the first element and the corresponding exponent as the second. If you set n=3, it produces engineering notation.

The ‘Result’ string is simply an sprintf call that you can change to produce the string you want.

Experiment with it.